1. Field of the Invention
The present invention relates to an apparatus and method for monitoring the optical properties of a magnetic recording head that is typically installed into a hard disk drive.
2. Description of Related Art
Hard disk drives contain magnetic recording heads which magnetize and sense the magnetic field of a rotating magnetic disk(s). The recording head is integrated into a slider which has hydrodynamic features that create an air bearing between the head and the disk. The air bearing prevents contact and corresponding mechanical wear of the recording head.
The sliders are typically tested in a flying height tester before being installed into a hard disk drive assembly. Flying height testers measure the height of the air bearing mom insure that the slider complies with manufacturing specifications. The sliders "fly" above a transparent disk that is rotated by a spindle. A beam of light is directed through the disk and reflected off of the disk/head interface. The reflected light creates an interference pattern that is detected and analyzed by the tester to determine the flying height of the slider.
The interference pattern is a function of the index of refraction n and the extinction coefficient k of the slider. It has .been found that the n and k values may vary from slider to slider. A variation in the optical properties may reduce the accuracy of the flying height tester. The actual n and k values of a slider can be measured using an ellipsometer. The actual values are then used by the flying height tester to measure the height of the air bearing.
A typical recording head contains a read/write element that is buried within a substrate. The trailing edge of the substrate may be constructed from an aluminum oxide (Al.sub.2 O.sub.3) material. The read/write element is constructed from metal materials such as copper and nickel/iron (NiFe).
The aluminum oxide is a relatively translucent material such that the slider area containing the read/write elements may have different effective n and k values than the remaining portion of the trailing edge. Additionally, manufacturing processes and tolerances may create n and k variations between different points of the slider. The variation in optical properties requires a small beam spot diameter for the flying height tester and a corresponding small beam spot for the ellipsometer to differentiate between the read/write element and the remaining area of the slider. Small beam diameters are difficult to produce. Additionally, small beam diameters increase the time required to measure the n and k values of the slider. It would be desirable to provide a relatively inexpensive apparatus and method for quickly monitoring the optical properties of a recording head.